ci: Use carpentries/actions/check-valid-pr@v0.14.0

This commit updates the CI workflows to use the check-valid-pr action
v0.14.0, which uses the up-to-date GitHub commands, in preparation for
the upcoming removal of the deprecated GitHub features.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>
(cherry picked from commit 7fe5c53b)